Tuning of diaphragms for generating or receiving sound-waves



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L. V. KING. TUNING 0F DIAPHRAGMS FOR GENERATING 0R RECEIVING SOUND IWAVES. APPLICATION FILED APR. 1. 1919.

1,375,707 I Patented p 26, 1921.

fig? UNITED STAT-ES PATENT OFFICE.

LOUIS VESSO'I KING, OF MONTREAL, QUEBEC, GANADA.

TUNING or nrarnaaems roa GENERATING on nncnrvnvc sonNn-wAvEs.

T all whom it may concern Be it known that I, LOUIS Vnsso'r KING, a subject of the King of Great Britain, and resident of the city of Montreal, Province of Quebec, Dominion of Canada, have invented certain new and useful Improvements in the Tuning of Diaphragms for Generating or Receiving Sound-Waves; and I do here- I by declare that the following is a full, clear,

and exact description thereof.

Heretofore it has not been possible to adjust from a distance at will and to meet continuously varying conditions, the fundamental pitch of diaphragins for the purpose of tuning the same to the frequency of the actuating vibratory force; neither has it been possible to know the change of volume for each pulsation and hence the acoustic load, and consequently, the characteristics of the diaphragm could not be accurately predetermined. To overcome these defects is the object of my invention and to this end I have provided a diaphragm of particular construction and combined with it means whereby it may be tuned at will and continuously from a distance within reasonable limits of pitch, andmeans whereby an electro-vibratoryforce is applied to a certain defined area of the diaphragm. u N More specifically stated the invention consists in a diaphragm having a solid and practically undeformable area connected to the means for-mounting-same by a relatively thin, flexible, or deformable portion. This diaphragm is mounted in a position on a suitable body presenting with the diaphragm an hermetically sealed gas chamber wlth means for supplying a-gaseous'pressure or suction thereto and, consequently, over the.

interior of the diaphragm, thereby causing it to bulge slightly outward or inward as h the ase may be. To'generate pulsatlons I 'equip the undeformableareafiof the diaphragm constltuting a component part of the diawith a vibrator of tubular form phragm and constructed and arranged to generate or receive pulsations to or from the I diaphragm without disturbing the continuity of tuning. Electrical pulsations are transformed into sound pulsations and viceversa' by an electroemagnetic mechanism forming the body upon and within which i this diaphragm, which I term a piston-diaphragm is mounted, The electrical devices illustrated in the drawings with my diaphragm and means Specification of Letters Patent. Pat t d APR 26 1921 Application filedApril 1, 1919. Serial No. 286,805,

for tuning the same applied thereto are well known and form no partof my invention. except in combination. I I

F or full comprehension, however, of my invention reference must be had'to-the accompanying' drawings in which similar reference characters indicate the same parts and wherein: I

Figure 1 illustrates diagrammatically a diaphragm fashioned according to my in- Fig. *5 illustrates diagrammatically a i microphone receiver and a telephone recelver arranged for the simultaneous unisonal tuning of their diaphragms; and

F1g. 6 is a sectional view taken on line 6.6 of Fig. 5;

I will now, describe in what manner the lnvention relates to a means of altering con tlnuously atwill from a distance, by the application of fluid pressure .(or suction) ob.

'' tained by the use of compressed (or rarefied) air or other gases, the fundamental pitch or frequency of the diaphragm formmg part of an apparatus for generating or receiving sound waves in any elastic medium such as air or water; and the mode of constructing such a diaphragm inorder that tuning by the aforesaid method may be efi'ected and the change of volume for each pulsation'and hence the acoustic. load be known and consequently the characteristics ofv the diaphragm may be predetermined.

. The essential feature of the invention is illustrated in Fig. 1 showing the diaphragm mounted in position on the body B, the

form of the latter may be varied to suit the fashioned from-a single piece of metal or other elastic substance having as high an elastic limit as possible. It consists of a solid central portion C and of a heavy rim It connected by a relat vely thin annulusA.

material of given elastic properties.

25 may be continuously 45 versal The relative dimensions of these parts may be calculated to give any frequency desired in practice, as well as to provide for a maximum range of tuning possible foiha e rim of the diaphragm fits very accurately on a slightly tapered mounting M of the body. By the application of gaseous pres sure (or suction) over the interior of the diaphragm (supposed to be in gas-tight connection with the body) it is caused to bulge slightly (outward or inward). As the solid center is practically undeformed by its dis placement relative to the rim, the distance between the outer edge of the former and. the inner edge of the latter is increased (or diminished) by an amount depending on the pressure (or suction) applied. The tension of the thin annulus is thus increased (or 2o diminished) and as a result the frequency of the vibration of the central part of the diaphragm about the new equilibrium position israised or lowered. By this means the fundamental pitch of the diaphragm adjusted between reasonable limits by an alteration of gaseous pressure. I

In the drawings accompanying the pres ent specification, Fig. 1 illustrates diagraminatically the diaphragm mounted in position on the body B showing the rim B, annulus A and solid center (I. Air pressure for the purpose of tuning may be admitted through any aperture in the body B, such as that at P. Fig. 2 illustrates the diaphragm forming the subject of the present invention embodied as part of a tunable microphone as actually constructed for receiving selec-' tively submarine .sounds. A microphone 40 button G of the carbon-granule variablefixed in position in the body by means of an insulating bushing 1 and terminates in a platinized contact E at the conducting base i of the microphone button G, which is thus.

included in a circuit consisting of the insulating copper wire and the external cop per tube surrounding it. The circuit is by this means completely projected against induction effects and stray currents which are otherwise diflicult to avoid when it is required to pick up very faint sounds.

Fig. 3 illustrates the tunable diaphragm forming part of the present invention adapted to an electromagnetic mechanism.- The magnetic circuit consists of three pieces F F and F of high permeability steel. E

I aven or and F are designed to inclose a field winding i so that an intense radial field may be produced in the ap between these pieces and the core F half of the field being in opposite directions. The pieces B and F are held in rigid connection by a non-magnetic piece B which carries a universal coupling by means of which a tube B is joined in gas-tight connection to the interior of the apparatus. This tube besides serving to transmit the pressure or suction applied to the diaphragm for tuning purposes, preferably serves also to carry three insulated wires, two of which carry direct current to the field winding (through plugs and sockets in the insulated bushings l l while the third is connected in similar manner to the armature windings- B, the return current being the copper tube itself. The armature winding D is wound in opposite directions on the core F to which alternating current of the desired frequency may be supplied. in the gap is the copper {vibrator V rigidly connected to the solid center of the diaphragm, substantially as shown. The solid center forms in this way what 1 term an extremely rigid piston diaphragm held in osition by the annulus A and heavy rims (and in air-tight connection) on the rigid field-piece B when alternating current is supplied to the armature winding D the current of the same frequency is induced in they copperyibrator V. Through the interaction of the magnetic field in the gap, the vibrator is subjected to a powerful alternating force which is transmitted to the diaphragm and to the water in which the apparatus is immersed, giving rise to submarine sound-waves whose frequency may be varied between certain limits. From theoretical considerations it may be shown that the apparatus will not radiate efiiciently unless the pitch of the diaphragm is tuned very closely to the frequency of the alternating current supplied. Hence if it is desired to transmit selectively submarine signals of various wave-lengths (as in radioteleg-" rapny) it is necessary to be able to tune the diaphragm to the frequency of the alternat ing current by adjusting the pressure on the diaphragm in the manner indicated.

Fig. 4 illustrates the diaphragm adapted to form part of a telephone receiver. A steel or soft-iron diaphragm constructed in the manner already described is mounted in gas- -tight connection on a chambered body B 'with telephone receivers. The alternating constructed of aluminium or some light-nonmagnetic alloy, the dlaphragm serving as a cap or closure for the chamber. The body B may contain any of the electromagnetic arrangements generally used in connection current which it is required to detect is brought tothe magnet .W. through the lines of force in each' accurately mounted wires incl'osed in a fnetal tube P connected to the body 13 in such a Way that air pressure or suction may be applied to the diaphragm. The diaphragm is caused to vibrate by the change of magnetic flux between the diaphragm and pole-pieces in the well known manner. By tuning the diaphragm (by the application of gaseous pressure or suction) or resonance with the alternating current the audibility may be greatly improved. In order to accommodate the magnets to the diaphragm when tuned these magnets, are mounted on a frame 10 and adjusted through this frame by a screw 12 to, in turn, adjust the air-gap between the poles of the magnets and the diaphragm thereby maintaining conditions of maximum sensitiveness. A cap of the telephone is indicated at 15.

The technical advantages which I claim v for this invention are as follows: 1. Multiplex aerial 01' submarine acoustic v signaling. Diaphragms form an essential part of aerial or submarine sound receivers or generators. It is, well known that a sound-generator will radiatevery little energy unless the frequency of the alternating forcecausing the diaphragm to vibrate is veryclose to the free period of the diaphragm. As a result, sound-generators can be operated efficiently only at a single frequency, that of the diaphragm. By the ,use of the specially shaped diaphragms tuned by compressed air as described above, it .-becomes possible to operate an aerial or submarine sound-generator efliciently over a considerable range of frequencies. The same remarks apply to the receptive properties of aerial or submarine sound-receivers, the best conditions for audibility being when the diaphragm is tuned to the frequency of the incident waves.

' ing 1S made possible. It thus becomes pos- It follows that by the use'of sound generating and receiving apparatus capable of tuning in and out (as in' wireless telegraphy) multiplex acoustic submarine signalsible to transmit submarine signals not only by code but by including in the code prearranged changes of frequency, a system which makes interpretation by another listener extremely difficult.

2. Amplification of telephone reception.

much increased when the frequency of the impressed electro-motive force coincides with that of the diaphragm. By constructing telephone-diaphragms capable of variable tuning in the manner described, it follows that in reception of signals of a musical chartapered mountlng.

acter (as in radio-telegraphy or acoustic submarine telegraphy) the telephone receiver itself may be tuned to the frequency of the incoming wave and thus constantly employed at maximum audibility.

3. Submarine detection.

fitting submarine microphones with diaphragms capable of continuous tuning inthe manner described. In these circumstances the enhanced sensitiveness (low damping) which is known to result from Lsharp tuning may be utilized to greatestadvantage by employing a telephone receiver whose diaphragm is also tunable by compressed air, conditions being-so adjusted that" the resonance-frequency is attained at the same pressure throughout the range of the'90 frequency desired v I wish it to be understood that'I do not limit myself to the application to the field ofacoustics of a diagram continuously tun-' able by the application of gaseous pressure which is the principal and essential element of my invention and which may be adapted to other uses without departing from thespirit of my inventive idea.

What I claim is as follows:

1. The combination with a diaphra having a practically rigid central effective area supported by a relatively thin annular surrounding portion Whose tension determines the pitch of the vibrations of the central area, and meanswhereby the said central area is adjusted by the application of; gaseous pressure or suction.

2. A diaphragm consisting of; a unitary solid of revolution having a solid central 11b portion and heavy rim connected by a relatively thin annulus.

3. The combination with a slightly tapered mounting of a diaphragm consisting of a unitary solid of revolution and having a solid central portion and heavy rim, the said rim being accurately fitted upon the 4:. An electro-magnetic mechanism com prisingas essential elements, pieces of high permeability steel inclosing a field winding-- and core, a non-magnetic connecting piece, primary winding carried by the core adapted to beconnected to a source of high frequency current, a tubularvibrator adapted to form a part of and be actuated by the electro-vibratory force generated, an acou'stic diaphragm, the central portion of which is connected directly to the said tubular vi-- brator, and means for tuning the pitch. of ,130

the diaphragm to the frequency of the electro-vibratory force, said diaphragm consisting of a unitary solid of revolution of the substance described and having a solid central portion and heavy rim. connected by a relatively thin annulus.

I 5. An electro-magnetic mechanism comprising as essential elements pieces of high permeability steel inclosing a field winding and core and non magnetic connection piece, primary windings carried by the core adapted to beconnected to a source of high frequency current, a tubular vibrator adapted to form a part of and be actuated by the tion therewith to impart thereto the pulsa-' tions due to the electro vibratory force.

. b; An electro-magnetic mechanism comprising as essential elements pieces of high permeability steel inclosing a field winding and core, a non-magnetic .connection piece carrying a unisonal coupling, primarywindings carried by the .coreadapted to be connected to a source of hightrequency current, a tubular vibrator adapted to torma part of and be actuated by the electro-vibratory force generated, an acoustic diaphragm the central portion of which is connected directly to the said tubular vibrator, said diaphragm consisting of a unitary solid of revolution and having a solid central portion and heavy rim connected by a relatively thin annulus, the said solid central portion having the tubular vibrator in operative relation therewith to impart thereto the pulsations due to the electro-vibratory force, with means for tuning the diaphragm by gaseous pressure or suction to the frequency of the electro-vibratory force. 7

'Z. The combination with a slightly tapered mounting, of a diaphragm consisting of a unitary solid of revolution of the substance described and having a solid central portion and heavy rim, the said rim being accurately fitted upon the tapered mounting, and the said mounting and diaphragm containing between them a. microphone contact for the purpose of electrically detecting acoustic vibration, and means whereby the diaphragm may be tuned continuously from a distance into unison with the incident vibrations.

lln testimony whereof I have signed my name to this specification in the presence of two witnesses.

LOUIS VESSOT KING.

Witnesses:

GORDON G. CooKE, WILLIAM J. C. HuwErsoN. 

